bashtage/arch: Release 5.0

Release 5.0 contains new features and backward-incompatible changes.

• All unit root tests are now immutable, and so properties such as trend cannot be set after the test is created.

• Added seed keyword argument to all bootstraps (e.g., IIDBootstrap and StationaryBootstrap) that allows a NumPy numpy.random.Generator to be used. The seed keyword argument also accepts legacy numpy.random.RandomState instances and integers. If an integer is passed, the random number generator is constructed by calling numpy.random.default_rng The seed keyword argument replaces the random_state keyword argument.
• The IIDBootstrap.random_state property has also been deprecated in favor of IIDBootstrap.generator.
• The IIDBootstrap.get_state and IIDBootstrap.set_state methods have been replaced by the IIDBootstrap.state property.

• Added seed keyword argument to all distributions (e.g., Normal and StudentsT) that allows a NumPy numpy.random.Generator to be used. The seed keyword argument also accepts legacy numpy.random.RandomState instances and integers. If an integer is passed, the random number generator is constructed by calling numpy.random.default_rng The seed keyword argument replaces the random_state keyword argument.
• The Normal.random_state property has also been deprecated in favor of Normal.generator.
• Added ARCHInMean mean process supporting (G)ARCH-in-mean models.
• Extended VolatilityProcess with VolatilityProcess.volatility_updaterthat contains a VolatilityUpdater to allow ARCHInMean to be created from different volatility processes.